EC
TS1210
TypeScriptERRORNotableSyntaxHIGH confidence

Code contained in a class is evaluated in JavaScript's strict mode which does...

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1210): Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'X'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.. This diagnostic is emitted by the TypeScript compiler when code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'X'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode..

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS1210 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1210
// Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'X'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.

expected output

error TS1210: Code contained in a class is evaluated in JavaScript's strict mode which does not allow this use of 'X'. For more information, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode.

Fix

Address the TypeScript diagnostic

WHEN When this error is reported by the compiler

Address the TypeScript diagnostic
// Run the TypeScript compiler for details:
npx tsc --noEmit
// Use the TypeScript playground to test your code:
// https://www.typescriptlang.org/play

Why this works

Review the full error message and location; the TypeScript handbook provides guidance on each error category.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev

← All TypeScript errors